Annual Report_Abridged - Second Version - FINAL

23 aiming at understanding the global magnetic activity of the Sun. Nishant Singh and his team are working on making more advanced models to further understand the nature of interaction between the surface gravity mode of the Sun and its magnetic fields. Conventional understandings on turbulent dynamo are also being revisited in light of recent studies where one aims to look for observational signatures which can be probed by modern data from the Sun. As the data from SUIT (Solar and Ultraviolet Imaging Telescope) on board the Aditya-L1 has started coming in, we plan to investigate the nature of various types of waves in solar atmospheres in order to understand the heatingmechanisms of solar corona. Observational SolarPhysics The Sun, our star, is the source of all life-giving energy and also of the ever-varying space weather. It also provides knowledge about fundamental Physics in conditions not possible on the Earth. The atmosphere of the Sun presents several intriguing, mysterious phenomena e.g. the strange existence of a million-degree temperature layer called the Corona that lies above cooler, lower atmospheric layers, such as the photosphere and chromosphere. Moreover, it continuously engulfs the interplanetary medium with charged particles through the solar wind. In addition, Sun also produces large explosions such as flares and coronal mass ejections. During the high solar activity phase, theremay be asmany as 20 or even more highly energetic explosions in a day which produces sudden release of magnetised plasma into the interplanetary space. They directly influence terrestrial life, space weather, and space-reliant technologies andmay cause electric power blackouts in countries at higher latitudes on Earth. Humankind stands to gain a lot fromthe study of these phenomena. The Solar Physics group at IUCAA led by Durgesh Tripathi works on the overall understanding of the dynamic coupling of the magnetized solar atmosphere. In the last few years, among others, the IUCAA group has proposed a unified scenario to explain the solar atmospheric heating and the origin of the solar wind; presented an alternative explanation for Doppler shifts Observations in the solar transition region and discovered evidences for further strengthening the support for nano- flare heated solar corona. Important studies of the Sun also need to be made through the radiation it emits at high energies, such as ultraviolet, extreme ultraviolet, and X-rays. These cannot be seen from the Earth due to their absorption in the atmosphere. For this the IUCAA solar and instrumentation group together have built the Solar Ultraviolet Imaging Telescope (SUIT) that is now operating onboard the successful Aditya-L1 mission to study the Sun from Space. As the observational data from SUIT starts coming in, the group is investigating the nature of various physical phenomena, including the explosions, occurring in the solar atmosphere to understand the dynamic coupling of the magnetised solar atmosphere.